Bsi bs en 62305 1 2011

BS EN 62305-1:2011

BSI Standards Publication

Protection against lightning
Part 1: General principles


BS EN 62305-1:2011

BRITISH STANDARD
National foreword



EUROPEAN STANDARD

EN 62305-1

NORME EUROPÉENNE
EUROPÄISCHE NORM

February 2011

ICS 29.020; 91.120.40

Supersedes EN 62305-1:2006 + corr. Nov.2006

English version

Protection against lightning Part 1: General principles

(IEC 62305-1:2010, modified)
Protection contre la foudre Partie 1: Principes généraux
(CEI 62305-1:2010, modifiée)

Blitzschutz Teil 1: Allgemeine Grundsätze
(IEC 62305-1:2010, modifiziert)

This European Standard was approved by CENELEC on 2011-01-13. CENELEC members are bound to comply
with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard
the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and notified
to the Central Secretariat has the same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus,
the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,
Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia,
Spain, Sweden, Switzerland and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Management Centre: Avenue Marnix 17, B - 1000 Brussels
© 2011 CENELEC -

All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 62305-1:2011 E

BS EN 62305-1:2011
EN 62305-1:2011

-2-

Foreword
The text of document 81/370/FDIS, future edition 2 of IEC 62305-1, prepared by IEC TC 81, Lightning
protection, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as
EN 62305-1 on 2011-01-13.
This European Standard supersedes EN 62305-1:2006 + corr. Nov.2006.
This EN 62305-1:2011 includes the
EN 62305-1:2006 + corr. Nov.2006:

following

significant

technical

changes

with

respect

to

1) It no longer covers protection of services connected to structures.
2) Isolated interfaces are introduced as protection measures to reduce failure of electric and electronic

systems.
3) First negative impulse current is introduced as a new lightning parameter for calculation purposes.
4) Expected surge overcurrents due to lightning flashes have been more accurately specified for low
voltage power systems and for telecommunication systems.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN and CENELEC shall not be held responsible for identifying any or all such patent
rights.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement

(dop)

2011-10-13

– latest date by which the national standards conflicting
with the EN have to be withdrawn

(dow)

2014-01-13

Annex ZA has been added by CENELEC.
__________

Endorsement notice
The text of the International Standard IEC 62305-1:2010 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards indicated:

[1] IEC 60664-1:2007

NOTE Harmonized as EN 60664-1:2007 (not modified).

[2] IEC 61000-4-5

NOTE Harmonized as EN 61000-4-5.

[7] IEC 61643-1

NOTE Harmonized as EN 61643-11.

[8] IEC 61643-21

NOTE Harmonized as EN 61643-21.

__________


BS EN 62305-1:2011
-3-

EN 62305-1:2011

Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced

document (including any amendments) applies.
NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.

Publication

Year

Title

EN/HD

Year

IEC 62305-2

2010

Protection against lightning Part 2: Risk management

EN 62305-2

2011

IEC 62305-3

2010

Protection against lightning EN 62305-3
Part 3: Physical damage to structures and life

hazard

2011

IEC 62305-4

2010

Protection against lightning EN 62305-4
Part 4: Electrical and electronic systems within
structures

2011


BS EN 62305-1:2011
–2–

62305-1 Ó IEC:2010(E)

CONTENTS
FOREWORD ................................................................................................................. 5
INTRODUCTION ............................................................................................................ 7
1

Scope ..................................................................................................................... 8

2

Normative references ............................................................................................... 8

3

Terms and definitions ............................................................................................... 8

4

Lightning current parameters .................................................................................. 14

5

Damage due to lightning ......................................................................................... 14
5.1

6

Damage to a structure.................................................................................... 14
5.1.1 Effects of lightning on a structure ........................................................ 14
5.1.2 Sources and types of damage to a structure ......................................... 16
5.2 Types of loss ................................................................................................. 16
Need and economic justification for lightning protection ............................................ 18

7

6.1 Need for lightning protection .......................................................................... 18
6.2 Economic justification of lightning protection ................................................... 19
Protection measures............................................................................................... 19

8

7.1 General ........................................................................................................ 19
7.2 Protection measures to reduce injury of living beings by electric shock ............. 19
7.3 Protection measures to reduce physical damage .............................................. 20
7.4 Protection measures to reduce failure of electrical and electronic systems ........ 20
7.5 Protection measures selection ........................................................................ 20
Basic criteria for protection of structures.................................................................. 21
8.1
8.2
8.3
8.4

General ........................................................................................................ 21
Lightning protection levels (LPL) .................................................................... 21
Lightning protection zones (LPZ) .................................................................... 23
Protection of structures .................................................................................. 25
8.4.1 Protection to reduce physical damage and life hazard ........................... 25
8.4.2 Protection to reduce the failure of internal systems ............................... 26
Annex A (informative) Parameters of lightning current ................................................... 27
Annex B (informative) Time functions of the lightning current for analysis purposes ........ 38
Annex C (informative) Simulation of the lightning current for test purposes ..................... 44
Annex D (informative) Test parameters simulating the effects of lightning on LPS
components ................................................................................................................. 48
Annex E (informative) Surges due to lightning at different installation points ................... 62
Bibliography ................................................................................................................ 67
Figure 1 – Connection between the various parts of IEC 62305 ......................................... 7
Figure 2 – Types of loss and corresponding risks resulting from different types of
damage ....................................................................................................................... 18
Figure 3 – LPZ defined by an LPS (IEC 62305-3) ........................................................... 24
Figure 4 – LPZ defined by an SPM (IEC 62305-4) .......................................................... 25
Figure A.1 – Definitions of impulse current parameters (typically T 2 < 2 ms) .................... 27

Figure A.2 – Definitions of long duration stroke parameters (typically 2 ms <1 s) ........................................................................................................................... 28


BS EN 62305-1:2011
62305-1 Ó IEC:2010(E)

–3–

Figure A.3 – Possible components of downward flashes (typical in flat territory and
to lower structures) ...................................................................................................... 28
Figure A.4 – Possible components of upward flashes (typical to exposed and/or
higher structures) ......................................................................................................... 29
Figure A.5 – Cumulative frequency distribution of lightning current parameters (lines
through 95 % and 5 % value) ........................................................................................ 34
Figure B.1 – Shape of the current rise of the first positive impulse .................................. 39
Figure B.2 – Shape of the current tail of the first positive impulse ................................... 40
Figure B.3 – Shape of the current rise of the first negativ e impulse ................................. 40
Figure B.4 – Shape of the current tail of the first negativ e impulse .................................. 41
Figure B.5 – Shape of the current rise of the subsequent negativ e impulses .................... 42
Figure B.6 – Shape of the current tail of the subsequent negativ e impulses ..................... 42
Figure B.7 – Amplitude density of the lightning current according to LPL I ....................... 43
Figure C.1 – Example test generator for the simulation of the specific energy of the
first positive impulse and the charge of the long stroke ................................................... 45
Figure C.2 – Definition of the current steepness in accordance with Table C.3 ................. 46
Figure C.3 – Example test generator for the simulation of the front steepness of the
first positive impulse for large test items ....................................................................... 47
Figure C.4 – Example test generator for the simulation of the front steepness of the
subsequent negativ e impulses for large test items .......................................................... 47
Figure D.1 – General arrangement of two conductors for the calculation of

electrodynamic force .................................................................................................... 54
Figure D.2 – Typical conductor arrangement in an LPS................................................... 55
Figure D.3 – Diagram of the stresses F for the configuration of Figure D.2....................... 55
Figure D.4 – Force per unit length F’ along the horizontal conductor of Figure D.2 ........... 56
Table 1 – Effects of lightning on typical structures ......................................................... 15
Table 2 – Damage and loss relevant to a structure according to different points of
strike of lightning ......................................................................................................... 17
Table 3 – Maximum values of lightning parameters according to LPL .............................. 22
Table 4 – Minimum values of lightning parameters and related rolling sphere radius
corresponding to LPL ................................................................................................... 22
Table 5 – Probabilities for the limits of the lightning current parameters .......................... 23
Table A.1 – Tabulated values of lightning current parameters taken from CIGRE
(Electra No. 41 or No. 69) [3], [4] .................................................................................. 31
Table A.2 – Logarithmic normal distribution of lightning current parameters – Mean
m and dispersion σ log calculated from 95 % and 5 % values from CIGRE (Electra No.
41 or No. 69) [3], [4] ..................................................................................................... 32
Table A.3 – Values of probability P as function of the lightning current I .......................... 33
Table B.1 – Parameters for Equation (B.1)..................................................................... 38
Table C.1 – Test parameters of the first positive impulse ................................................ 45
Table C.2 – Test parameters of the long stroke .............................................................. 45
Table C.3 – Test parameters of the impulses ................................................................. 46
Table D.1 – Summary of the lightning threat parameters to be considered in the
calculation of the test values for the different LPS components and for the different
LPL 49
Table D.2 – Physical characteristics of typical materials used in LPS components ............ 52


BS EN 62305-1:2011
–4–

62305-1 Ó IEC:2010(E)

Table D.3 – Temperature rise for conductors of different sections as a function of
W/R ............................................................................................................................ 52
Table E.1 – Conventional earthing impedance values Z and Z 1 according to the
resistiv ity of the soil ..................................................................................................... 63
Table E.2 – Expected surge overcurrents due to lightning flashes on low-v oltage
systems ....................................................................................................................... 64
Table E.3 – Expected surge overcurrents due to lightning flashes on
telecommunication systems .......................................................................................... 65


BS EN 62305-1:2011
62305-1 Ó IEC:2010(E)

–5–

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PROTECTION AGAINST LIGHTNING –
Part 1: General principles

FOREW ORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and in
addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,
Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their
preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
may participate in this preparatory work. International, governmental and non-governmental organizations liaising

with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for
Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. W hile all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence between
any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 62305-1 has been prepared by IEC technical committee 81:
Lightning protection.
This second edition cancels and replaces the first edition, published in 2006, and
constitutes a technical rev ision.

This edition includes the following significant technical changes with respect to the previous
edition:
1) It no longer cov ers protection of services connected to structures.
2) Isolated interfaces are introduced as protection measures to reduce failure of electric
and electronic systems.
3) First negative impulse current is introduced as a new lightning parameter for calculation
purposes.
4) Expected surge overcurrents due to lightning flashes have been more accurately
specified for low voltage power systems and for telecommunication systems.


BS EN 62305-1:2011
62305-1 Ó IEC:2010(E)

–6–
The text of this standard is based on the following documents:
FDIS

Report on voting

81/370/FDIS

81/380/RVD

Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the abov e table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all the parts in the IEC 62305 series, under the general title Protection against
lightning, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until

the stability date indicated on the IEC web site under "" in the data
related to the specific publication. At this date, the publication will be
•
•
•
•

reconfirmed,
withdrawn,
replaced by a rev ised edition, or
amended.

A bilingual version of this standard may be issued at a later date.


BS EN 62305-1:2011
62305-1 Ó IEC:2010(E)

–7–

INTRODUCTION
There are no devices or methods capable of modifying the natural weather phenomena to
the extent that they can prev ent lightning discharges. Lightning flashes to, or nearby,
structures (or lines connected to the structures) are hazardous to people, to the structures
themselves, their contents and installations as well as to lines. This is why the application
of lightning protection measures is essential.
The need for protection, the economic benefits of installing protection measures and the
selection of adequate protection measures should be determined in terms of risk
management. Risk management is the subject of IEC 62305-2.
Protection measures considered in IEC 62305 are proved to be effective in risk reduction.

All measures for protection against lightning form the overall lightning protection. For
practical reasons the criteria for design, installation and maintenance of lightning protection
measures are considered in two separate groups:
–

the first group concerning protection measures to reduce physical damage and life
hazard in a structure is giv en in IEC 62305-3;

–

the second group concerning protection measures to reduce failures of electrical and
electronic systems in a structure is giv en in IEC 62305-4.

The connection between the parts of IEC 62305 is illustrated in Figure 1.

The lightning threat

IEC 62305-1

IEC 62305-2

Lightning risk

L

Lightning protection

LPS

Protection measures

IEC 62305-3

SPM

IEC 62305-4
IEC

2612/10

Figure 1 – Connection between the various parts of IEC 62305


BS EN 62305-1:2011
–8–

62305-1 Ó IEC:2010(E)

PROTECTION AGAINST LIGHTNING –
Part 1: General principles

1

Scope

This part of IEC 62305 prov ides general principles to be followed for protection of structures
against lightning, including their installations and contents, as well as persons.
The following cases are outside the scope of this standard:
–

railway systems;

–

vehicles, ships, aircraft, offshore installations;

–

underground high pressure pipelines;

-

pipe, power and telecommunication lines placed outside the structure.

NOTE

2

These systems usually fall under special regulations produced by various specialized authorities.

Normative references

The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest
edition of the referenced document (including any amendments) applies.
IEC 62305-2:2010, Protection against lightning – Part 2: Risk management
IEC 62305-3:2010, Protection against lightning – Part 3: Physical damage to structures and
life hazard
IEC 62305-4:2010, Protection against lightning – Part 4: Electrical and electronic systems
within structures

3

Terms and definitions

For the purposes of this document, the following terms and definitions apply.
3.1
lightning flash to earth
electrical discharge of atmospheric origin between cloud and earth consisting of one or
more strokes
3.2
downward flash
lightning flash initiated by a downward leader from cloud to earth
NOTE A downward flash consists of a first impulse, which can be followed by subsequent impulses. One or more
impulses may be followed by a long stroke.

3.3
upward flash
lightning flash initiated by an upward leader from an earthed structure to cloud


BS EN 62305-1:2011
62305-1 Ó IEC:2010(E)

–9–

NOTE An upward flash consists of a first long stroke with or without multiple superimposed impulses. One or more
impulses may be followed by a long stroke.

3.4

lightning stroke
single electrical discharge in a lightning flash to earth
3.5
short stroke
part of the lightning flash which corresponds to an impulse current
NOTE

This current has a time T 2 to the half peak value on the tail typically less than 2 ms (see Figure A.1).

3.6
long stroke
part of the lightning flash which corresponds to a continuing current
NOTE The duration time T LONG (time from the 10 % value on the front to the 10 % value on the tail) of this
continuing current is typically more than 2 ms and less than 1 s (see Figure A.2).

3.7
multiple strokes
lightning flash consisting on average of 3-4 strokes, with typical time interv al between them
of about 50 ms
NOTE Events having up to a few dozen strokes with intervals between them ranging from 10 ms to 250 ms have
been reported.

3.8
point of strike
point where a lightning flash strikes the earth, or protruding structure (e.g. structure, LPS,
line, tree, etc.)
NOTE

A lightning flash may have more than one point of strike.

3.9
lightning current
i
current flowing at the point of strike
3.10
current peak value
I
maximum value of the lightning current
3.11
average steepness of the front of impulse current
average rate of change of current within a time interv al Δt = t 2 – t 1
NOTE It is expressed by the difference Δi = i(t 2 ) – i(t 1 ) of the values of the current at the start and at the end of this
interval, divided by the time interval Δt = t 2 – t 1 (see Figure A.1).

3.12
front time of impulse current
T1
virtual parameter defined as 1,25 times the time interv al between the instants when the
10 % and 90 % of the peak value are reached (see Figure A.1)


BS EN 62305-1:2011
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62305-1 Ó IEC:2010(E)

3.13
virtual origin of impulse current
O1
point of intersection with time axis of a straight line drawn through the 10 % and the 90 %

reference points on the stroke current front (see Figure A.1); it precedes by 0,1 T 1 that
instant at which the current attains 10 % of its peak value
3.14
time to half value on the tail of impulse current
T2
virtual parameter defined as the time interv al between the v irtual origin O 1 and the instant
at which the current has decreased to half the peak v alue on the tail (see Figure A.1)
3.15
flash duration
T
time for which the lightning current flows at the point of strike
3.16
duration of long stroke current
T LONG
time duration during which the current in a long stroke is between 10 % of the peak v alue
during the increase of the continuing current and 10 % of the peak value during the
decrease of the continuing current (see Figure A.2)
3.17
flash charge
Q FLASH
value resulting from the time integral of the lightning current for the entire lightning flash
duration
3.18
impulse charge
Q SHORT
value resulting from the time integral of the lightning current in an impulse
3.19
long stroke charge
Q LONG
value resulting from the time integral of the lightning current in a long stroke

3.20
specific energy
W/R
value resulting from the time integral of the square of the lightning current for the entire
flash duration
NOTE

It represents the energy dissipated by the lightning current in a unit resistance.

3.21
specific energy of impulse current
value resulting from the time integral of the square of the lightning current for the duration
of the impulse
NOTE

The specific energy in a long stroke current is negligible.


BS EN 62305-1:2011
62305-1 Ó IEC:2010(E)

– 11 –

3.22
structure to be protected
structure for which protection is required against the effects of lightning in accordance with
this standard
NOTE

A structure to be protected may be part of a larger structure.

3.23
line
power line or telecommunication line connected to the structure to be protected
3.24
telecommunication lines
lines intended for communication between equipment that may be located in separate
structures, such as a phone line and a data line
3.25
power lines
distribution lines feeding electrical energy into a structure to power electrical and electronic
equipment located there, such as low voltage (LV) or high voltage (HV) electric mains
3.26
lightning flash to a structure
lightning flash striking a structure to be protected
3.27
lightning flash near a structure
lightning flash striking close enough to a structure to be protected that it may cause
dangerous overv oltages
3.28
electrical system
system incorporating low voltage power supply components
3.29
electronic system
system incorporating sensitive electronic components such as telecommunication
equipment, computer, control and instrumentation systems, radio systems, power electronic
installations
3.30
internal systems
electrical and electronic systems within a structure

3.31
physical damage
damage to a structure (or to its contents) due to mechanical, thermal, chemical and
explosive effects of lightning
3.32
injury of living beings
permanent injuries, including loss of life, to people or to animals by electric shock due to
touch and step v oltages caused by lightning
NOTE Although living beings may be injured in other ways, in this standard the term ‘injury to living beings’ is
limited to the threat due to electrical shock (type of damage D1).


BS EN 62305-1:2011
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62305-1 Ó IEC:2010(E)

3.33
failure of electrical and electronic systems
permanent damage of electrical and electronic systems due to LEMP
3.34
lightning electromagnetic impulse
LEMP
all electromagnetic effects of lightning current via resistive, inductive and capacitive
coupling that create surges and radiated electromagnetic fields
3.35
surge
transient created by LEMP that appears as an overv oltage and/or an overcurrent
3.36
lightning protection zone

LPZ
zone where the lightning electromagnetic environment is defined
NOTE

The zone boundaries of an LPZ are not necessarily physical boundaries (e.g. walls, floor and ceiling).

3.37
risk
R
value of probable average annual loss (humans or goods) due to lightning, relative to the
total value (humans or goods) of the structure to be protected
3.38
tolerable risk
RT
maximum value of the risk which can be tolerated for the structure to be protected
3.39
lightning protection level
LPL
number related to a set of lightning current parameters values relevant to the probability
that the associated maximum and minimum design v alues will not be exceeded in naturally
occurring lightning
NOTE Lightning protection level is used to design protection measures according to the relevant set of lightning
current parameters.

3.40
protection measures
measures to be adopted for the structure to be protected in order to reduce the risk
3.41
lightning protection
LP

complete system for protection of structures against lightning, including their internal
systems and contents, as well as persons, in general consisting of an LPS and SPM
3.42
lightning protection system
LPS
complete system used to reduce physical damage due to lightning flashes to a structure
NOTE

It consists of both external and internal lightning protection systems.


BS EN 62305-1:2011
62305-1 Ó IEC:2010(E)

– 13 –

3.43
external lightning protection system
part of the LPS consisting of an air-termination system, a down-conductor system and an
earth-termination system
3.44
internal lightning protection system
part of the LPS consisting of lightning equipotential bonding and/or electrical insulation of
external LPS
3.45
air-termination system
part of an external LPS using metallic elements such as rods, mesh conductors or catenary
wires intended to intercept lightning flashes
3.46
down-conductor system

part of an external LPS intended to conduct lightning current from the air-termination
system to the earth-termination system
3.47
earth-termination system
part of an external LPS which is intended to conduct and disperse lightning current into the
earth
3.48
external conductive parts
extended metal items entering or leaving the structure to be protected such as pipe works,
cable metallic elements, metal ducts, etc. which may carry a part of the lightning current
3.49
lightning equipotential bonding
EB
bonding to LPS of separated metallic parts, by direct conductive connections or v ia surge
protective devices, to reduce potential differences caused by lightning current
3.50
conventional earthing impedance
ratio of the peak values of the earth-termination voltage and the earth-termination current
which, in general, do not occur simultaneously
3.51
LEMP protection measures
SPM
measures taken to protect internal systems against the effects of LEMP
NOTE

This is part of overall lightning protection.

3.52
magnetic shield
closed, metallic, grid-like or continuous screen enveloping the structure to be protected, or

part of it, used to reduce failures of electrical and electronic systems
3.53
surge protective device
SPD
device intended to limit transient overv oltages and divert surge currents; contains at least
one non linear component


BS EN 62305-1:2011
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62305-1 Ó IEC:2010(E)

3.54
coordinated SPD system
SPDs properly selected, coordinated and installed to form a system intended to reduce
failures of electrical and electronic systems
3.55
rated impulse withstand voltage
UW
impulse withstand v oltage assigned by the manufacturer to the equipment or to a part of it,
characterizing the specified withstand capability of its insulation against overv oltages
NOTE

For the purposes of this standard, only withstand voltage between live conductors and earth is considered.

[IEC 60664-1:2007, definition 3.9.2]

[1]

1

3.56
isolating interfaces
devices which are capable of reducing conducted surges on lines entering the LPZ
NOTE 1 These include isolation transformers with earthed screen between windings, metal free fibre optic
cables and opto-isolators.
NOTE 2
SPD.

4

Insulation withstand characteristics of these devices are suitable for this application intrinsically or via

Lightning current parameters

The lightning current parameters used in the IEC 62305 series are given in Annex A.
The time function of the lightning current to be used for analysis purposes is given in
Annex B.
Information for simulation of lightning current for test purposes is giv en in Annex C.
The basic parameters to be used in laboratories to simulate the effects of lightning on LPS
components are given in Annex D.
Information on surges due to lightning at different installation points is given in Annex E.

5

Damage due to lightning

5.1

Damage to a structure

Lightning affecting a structure can cause damage to the structure itself and to its occupants
and contents, including failure of internal systems. The damages and failures may also
extend to the surroundings of the structure and even involve the local environment.
The scale of this extension depends on the characteristics of the structure and on the
characteristics of the lightning flash.
5.1.1

Effects of lightning on a structure

The main characteristics of structures relevant to lightning effects include:
- construction (e.g. wood, brick, concrete, reinforced concrete, steel frame construction);
___________
1 References in square brackets refer to the bibliography.


BS EN 62305-1:2011
62305-1 Ó IEC:2010(E)

– 15 –

- function (dwelling house, office, farm, theatre, hotel, school, hospital, museum, church,
prison, department store, bank, factory, industry plant, sports area);
- occupants and contents (persons and animals, presence of combustible or noncombustible materials, explosive or non-explosive materials, electrical and electronic
systems with low or high withstand v oltage);
- connected lines (power lines, telecommunication lines, pipelines);
- existing or prov ided protection measures (protection measures to reduce physical
damage and life hazard, protection measures to reduce failure of internal systems);
- scale of the extension of danger (structure with difficulty of ev acuation or structure where

panic may be created, structure dangerous to the surroundings, structure dangerous to
the environment).
Table 1 reports the effects of lightning on v arious types of structures.
Table 1 – Effects of lightning on typical structures
Type of structure according to
function and/or contents

Effects of lightning

Dwelling-house

Puncture of electrical installations, fire and material damage
Damage normally limited to structures exposed to the point of strike or to the
lightning current path
Failure of electrical and electronic equipment and systems installed (e.g. TV
sets, computers, modems, telephones, etc.)

Farm building

Primary risk of fire and hazardous step voltages as well as material damage
Secondary risk due to loss of electric power, and life hazard to livestock due to
failure of electronic control of ventilation and food supply systems, etc.

Theatre
Hotel
School

Damage to the electrical installations (e.g. electric lighting) likely to cause
panic
Failure of fire alarms resulting in delayed fire fighting measures

Department store
Sports area
Bank
Insurance company

As above, plus problems resulting from loss of communication, failure of
computers and loss of data

Commercial company, etc.
Hospital
Nursing home

As above, plus problems of people in intensive care, and the difficulties of
rescuing immobile people

Prison
Industry

Additional effects depending on the contents of factories, ranging from minor
to unacceptable damage and loss of production

Museums and archaeological site

Loss of irreplaceable cultural heritage

Church
Telecommunication

Unacceptable loss of services to the public

Power plants
Firework factory

Consequences of fire and explosion to the plant and its surroundings

Munitions works
Chemical plant
Refinery
Nuclear plant
Biochemical laboratories and plants

Fire and malfunction of the plant with detrimental consequences to the local
and global environment


BS EN 62305-1:2011
– 16 –
5.1.2

62305-1 Ó IEC:2010(E)

Sources and types of damage to a structure

The lightning current is the source of damage. The following situations shall be taken into
account, depending on the position of the point of strike relative to the structure considered:
a)

S1: flashes to the structure;

b)

S2: flashes near the structure;

c)

S3: flashes to the lines connected to the structure;

d)

S4: flashes near the lines connected to the structure.

a)

Flashes to the structure can cause:

–

immediate mechanical damage, fire and/or explosion due to the hot lightning plasma arc
itself, due to the current resulting in ohmic heating of conductors (ov er-heated
conductors), or due to the charge resulting in arc erosion (melted metal);

–

fire and/or explosion triggered by sparks caused by overv oltages resulting from resistive
and inductive coupling and to passage of part of the lightning currents;

–

injury to living beings by electric shock due to step and touch voltages resulting from

resistive and inductive coupling;

–

failure or malfunction of internal systems due to LEMP.

b)

Flashes near the structure can cause:

–

failure or malfunction of internal systems due to LEMP.

c)

Flashes to a line connected to the structure can cause:

–

fire and/or explosion triggered by sparks due to overv oltages and lightning currents
transmitted through the connected line;

–

injury to living beings by electric shock due to touch v oltages inside the structure
caused by lightning currents transmitted through the connected line;

–

failure or malfunction of internal systems due to overv oltages appearing on connected
lines and transmitted to the structure.

d)
–

Flashes near a line connected to the structure can cause:
failure or malfunction of internal systems due to overv oltages induced on connected
lines and transmitted to the structure.

NOTE 1 Malfunctioning of internal systems is not covered by the IEC 62305 series. Reference should be made to
[2]
IEC 61000-4-5
.
NOTE 2

Only the sparks carrying lightning current (total or partial) are regarded as able to trigger fire.

NOTE 3 Lightning flashes, direct to or near the incoming pipelines, do not cause damages to the structure,
provided that they are bonded to the equipotential bar of the structure (see IEC 62305-3).

As a result, the lightning can cause three basic type of damage:
-

D1: injury to living beings by electric shock;

-

D2: physical damage (fire, explosion, mechanical destruction, chemical release) due to
lightning current effects, including sparking;

-

D3: failure of internal systems due to LEMP.

5.2

Types of loss

Each type of damage relevant to structure to be protected, alone or in combination with
others, may produce different consequential loss. The type of loss that may appear depends
on the characteristics of the structure itself.


BS EN 62305-1:2011
62305-1 Ó IEC:2010(E)

– 17 –

For the purposes of IEC 62305, the following types of loss, which may appear as
consequence of damages relevant to structure, are considered:
-

L1: loss of human life (including permanent injury);

-

L2: loss of serv ice to the public;

-

L3: loss of cultural heritage;

-

L4: loss of economic value (structure, its content, and loss of activity).

NOTE For the purposes of IEC 62305, only utilities such as gas,water,TV, TLC and power supply are considered
service to the public.

Losses of type L1, L2 and L3 may be considered as loss of social values, whereas a loss of
type L4 may be considered as purely an economic loss.
The relationship between source of damage, type of damage and loss is reported in Table
2.
Table 2 – Damage and loss relevant to a structure according to
different points of strike of lightning
Point of strike

Structure

Source of damage

S1

Near a structure

S2

Line connected to the
structure

S3

Near a line

S4

Type of damage

Type of loss

D1

L1 , L4 a

D2

L1, L2, L3, L4

D3

L1 b , L2, L4

D3

L1 b , L2, L4

D1

L1, L4 a

D2

L1, L2, L3, L4

D3

L1 b , L2, L4

D3

L1 b , L2, L4

a

Only for properties where animals may be lost..

b

Only for structures with risk of explosion and for hospitals or other structures where failure of internal systems
immediately endangers human life.


BS EN 62305-1:2011
62305-1 Ó IEC:2010(E)

– 18 –

Types of loss resulting from types of damage and the corresponding risks are reported in
Figure 2.

Type of
loss

Type of
damage

Injury
to living
beings
by electric
shock

Risk
R1

Risk
R2

Risk
R3

Risk
R4

Loss of
human life

Loss of
service to

the public

Loss of
cultural
heritage

Loss of
economic
values

2)

1)

Physical
damage

Failure
of internal
systems

Physical
damage

Failure
of internal
systems

Physical
damage

Injury
to living
beings
by electric
shock

Physical
damage

Failure
of internal
systems

IEC 2613/10

a
b

Only for hospitals or other structures where failure of internal systems immediately endanger human life.
Only for properties where animals may be lost.

Figure 2 – Types of loss and corresponding risks resulting
from different types of damage

6
6.1

Need and economic justification for lightning protection
Need for lightning protection

The need for the lightning protection of a structure to be protected in order to reduce the
loss of social values L1, L2 and L3 shall be evaluated.
In order to evaluate whether or not lightning protection of a structure is needed, a risk
assessment in accordance with the procedures contained in IEC 62305-2 shall be made.
The following risks shall be taken into account, corresponding to the types of loss reported
in 5.2:
-

R 1 : risk of loss or permanent injury of human life;

-

R 2 : risk of loss of services to the public;

-

R 3 : risk of loss of cultural heritage.

NOTE 1 Risk R 4 : risk of loss of economic values, should be assessed whenever the economic justification of
lightning protection is considered (see 6.2).

Protection against lightning is needed if the risk R (R 1 to R 3 ) is higher than the tolerable
level R T
R > RT
In this case, protection measures shall be adopted in order reduce the risk R (R 1 to R 3 ) to
the tolerable level R T
R £ RT

BS EN 62305-1:2011
62305-1 Ó IEC:2010(E)

– 19 –

If more than one type of loss could appear, the condition R £ R T shall be satisfied for each
type of loss (L1, L2 and L3).
The values of tolerable risk R T where lightning could result in the loss of items of social
value should be under the responsibility of a competent national body.
NOTE 2 An authority having jurisdiction may specify the need for lightning protection for specific applications
without requiring a risk assessment. In these cases, the required lightning protection level will be specified by the
authority having jurisdiction. In some cases, a risk assessment may be performed as a technique by which to justify
a waiver to these requirements.
NOTE 3 Detailed information on risk assessment and on the procedure for selection of protection measures is
reported in IEC 62305-2.

6.2

Economic justification of lightning protection

Besides the need for lightning protection for the structure to be protected, it may be useful
to ev aluate the economic benefits of prov iding protection measures in order to reduce the
economic loss L4.
In this case, the risk R 4 of loss of economic v alues should be assessed. The assessment of
risk R 4 allows for the ev aluation of the cost of the economic loss with and without the
adopted protection measures.
Lightning protection is cost effective if the sum of the cost C RL of residual loss in the
presence of protection measures and the cost C PM of protection measures is lower than the
cost C L of total loss without protection measures:

C RL + C PM < C L
NOTE Detailed information on the evaluation of economic justification of lightning protection is reported in
IEC 62305-2.

7
7.1

Protection measures
General

Protection measures may be adopted in order to reduce the risk according to the type of
damage.
7.2

Protection measures to reduce injury of living beings by electric shock

Possible protection measures include:
–

adequate insulation of exposed conductive parts;

–

equipotentialization by means of a meshed earthing system;

-

physical restrictions and warning notices;

-

lightning equipotential bonding (EB).

NOTE 1 Equipotentialization and an increase of the contact resistance of the ground surface inside and outside the
structure may reduce the life hazard (see Clause 8 of IEC 62305-3:2010).
NOTE 2

Protection measures are effective only in structures protected by an LPS.

NOTE 3

The use of storm detectors and the associated provision taken may reduce the life hazard.


BS EN 62305-1:2011
– 20 –
7.3

62305-1 Ó IEC:2010(E)

Protection measures to reduce physical damage

Protection is achieved by the lightning protection system (LPS) which includes the following
features:
–

air-termination system;

–

down-conductor system;

–

earth-termination system;

–

lightning equipotential bonding (EB);

–

electrical insulation (and hence separation distance) against the external LPS.

NOTE 1 W hen an LPS is installed, equipotentialization is a very important measure to reduce fire and explosion
danger and life hazard. For more details see IEC 62305-3.
NOTE 2 Provisions limiting the development and propagation of the fire such as fireproof compartments,
extinguishers, hydrants, fire alarms and fire extinguishing installations may reduce physical damage.
NOTE 3

7.4

Protected escape routes provide protection for personnel.

Protection measures to reduce failure of electrical and electronic systems

Possible protection measures (SPM) include
·

earthing and bonding measures,

·

magnetic shielding,

·

line routing,

·

isolating interfaces,

·

coordinated SPD system.

These measures may be used alone or in combination.
NOTE 1 W hen source of damage S1 is considered, protection measures are effective only in structures protected
by an LPS.
NOTE 2 The use of storm detectors and the associated provision taken may reduce failures of electrical and
electronic systems.

7.5

Protection measures selection

The protection measures listed in 7.2, 7.3 and 7.4 together form the overall lightning
protection.
Selection of the most suitable protection measures shall be made by the designer of the

protection measures and the owner of the structure to be protected according to the type
and the amount of each kind of damage, the technical and economic aspects of the
different protection measures and the results of risk assessment.
The criteria for risk assessment and for selection of the most suitable protection measures
are given in IEC 62305-2.
Protection measures are effective prov ided that they comply with the requirements of
relevant standards and are able to withstand the stress expected in the place of their
installation.


BS EN 62305-1:2011
62305-1 Ó IEC:2010(E)

8
8.1

– 21 –

Basic criteria for protection of structures
General

An ideal protection for structures would be to enclose the structure to be protected within an
earthed and perfectly conducting continuous shield of adequate thickness, and to prov ide
adequate bonding, at the entrance point into the shield, of the lines connected to the
structure.
This would prev ent the penetration of lightning current and related electromagnetic field
into the structure to be protected and prev ent dangerous thermal and electrodynamic
effects of current, as well as dangerous sparkings and overv oltages for internal systems.
In practice, it is often neither possible nor cost effective to go to such measures to prov ide
such full protection.

Lack of continuity of the shield and/or its inadequate thickness allows the lightning current
to penetrate the shield causing:
–

physical damage and life hazard;

–

failure of internal systems.

Protection measures, adopted to reduce such damages and relevant consequential loss,
shall be designed for the defined set of lightning current parameters against which
protection is required (lightning protection level).
8.2

Lightning protection levels (LPL)

For the purposes of IEC 62305, four lightning protection levels (I to IV) are introduced. For
each LPL, a set of maximum and minimum lightning current parameters is fixed.
NOTE 1 Protection against lightning whose maximum and minimum lightning current parameters exceed those
relevant to LPL I needs more efficient measures which should be selected and erected on an individual basis.
NOTE 2 The probability of occurrence of lightning with minimum or maximum current parameters outside the range
of values defined for LPL I is less than 2 %.

The maximum values of lightning current parameters relevant to LPL I shall not be
exceeded, with a probability of 99 %. According to the polarity ratio assumed (see Clause
A.2), values taken from positive flashes will have probabilities below 10 %, while those from
negative flashes will remain below 1 % (see Clause A.3).
The maximum values of lightning current parameters relevant to LPL I are reduced to 75 %
for LPL II and to 50 % for LPL III and IV (linear for I, Q and di/dt, but quadratic for W/R).

The time parameters are unchanged.
NOTE 3 Lightning protection levels whose maximum lightning current parameters are lower than those relevant to
LPL IV allow one to consider values of probability of damage higher than those presented in Annex B of
IEC 62305-2:2010, but not quantified and are useful for better tailoring of protection measures in order to avoid
unjustified costs.

The maximum values of lightning current parameters for the different lightning protection
levels are given in Table 3 and are used to design lightning protection components (e.g.
cross-section of conductors, thickness of metal sheets, current capability of SPDs,
separation distance against dangerous sparking) and to define test parameters simulating
the effects of lightning on such components (see Annex D).
The minimum values of lightning current amplitude for the different LPL are used to derive
the rolling sphere radius (see Clause A.4) in order to define the lightning protection zone
LPZ 0 B which cannot be reached by direct strike (see 8.3 and Figures 3 and 4). The